=IF(C2="",B2,A1)
=GROUPBY(SCAN("",A2:A16,LAMBDA(x,y,IF(ISNUMBER(y),y,x))),B2:B16,SUM)
=GROUPBY(
SCAN("",A2:A16,LAMBDA(x,y,IF(ISNUMBER(y),y,x))),
B2:B16,SUM
)